Redefining phenotypes: human nature, or Nature itself?

Marcia Angell has the first of a disturbing two-part article on the doping of America in the current issue of the New York Review of Books.  It is a reflection of the nature of science in our society, of the challenge of complex biological traits and their genetic basis, and on the way we try to work out challenges to research when they are inevitably embedded in a large, integrated society.

She poses a number of questions, drawn from the three books on the current state of mental health and mental health care that she reviews.  She points out that prevalence of mental illness has risen sharply in the past few decades.

What is going on here? Is the prevalence of mental illness really that high and still climbing? Particularly if these disorders are biologically determined and not a result of environmental influences, is it plausible to suppose that such an increase is real? Or are we learning to recognize and diagnose mental disorders that were always there? On the other hand, are we simply expanding the criteria for mental illness so that nearly everyone has one? And what about the drugs that are now the mainstay of treatment? Do they work? If they do, shouldn’t we expect the prevalence of mental illness to be declining, not rising?

One issue that she raises is that the phenotype keeps changing.  We become more aware of a problem, we examine people more closely to get more sensitively detected aspects of their traits (in this case, behavioral or psychological). As a result we move asymptotically to a point at which everyone will have some form or other of diseases that needs particular treatment--often continued sessions with counselors, physicians, trainers, tutors, or years on maintenance meds.  We can see that some disorders are rising rapidly in incidence, but have a difficult time determining the extent to which this is 'true' or is a matter of our redefining the nature and detectability of the phenotypes.  (This is true of traits like autism as well--is autism really more prevalent now, or simply more frequently noticed and diagnosed?)

In a kind of naturally accelerating evolution of vested interests (special education funds, pharmaceutical profits, research topics for professors and news topics for journalists, and funding portfolios for bureaucrats), pressure not to eliminate these diseases might develop.  This may not be an inevitable aspect of society, but it does seem to be a kind of built-in rachet in our type of society, with little sense that we can ratchet down without some major crisis to distract us from the luxury of personalized disease and 'care'.

This is artificial and something to be noted and, we think, resisted.  But there is an interesting relevance to topics we discuss here on MT and evolution.  Environments, whatever they be, are always changing.  Sometimes this is glacially slow, other times rapid.  For each individual, what counts as 'environment' is local, specific, and need not be similar to what counts as such for a different individual.  From Darwin to the present, the theory of evolution is that natural selection is based on relative fitness.  The relative number of copies of a genetic variant next generation depends on its relative reproductive abilities in this generation.

This fact--or this notion, at least--by its own nature implies that the environment basically must continually change.  That is because natural selection changes genotype frequencies and that, by definition, changes the 'environment' of each individual!  With perhaps some technical exceptions (e.g., 'balancing selection' for readers familiar with that concept) this environmental flux is ineluctable, at least because the relative proportion of each type of competitor, not to mention how they modify what in the physical environment is available to an individual, by definition changes when selection is operating.

So what? you might ask!  So what is that even in Nature the definition of the phenotype, and its success in the life of each individual, is changing all the time.  Just as culture defines the phenotype when it comes to social position, treatment, privilege or disadvantage, and so on, so Nature defines the phenotype in terms of the adaptive and evolutionary future of its underlying genotype.

In either case, and perhaps unavoidably, we face an ever-changing landscape of what genes do and how it matters.